ERBIL, Kurdistan Region — Foreigners, fighting within the ISIS group, have made things on the ground worse for Iraqi and Syrian civilians, according to the US-led global anti-ISIS coalition.

"Foreign fighters have no reluctance whatsoever to treat civilians very poorly, so they use scorched earth tactics that we've seen before,” the coalition’s spokesman Col. John Dorrian told British reporters in a teleconference.”

Three foreigners surrendered to Turkish border police after more than two years in ISIS-controlled areas, the British daily, The Guardian, reported citing sources and Turkish officials.

"There are a significant number of foreign fighters in Mosul. One of the things we've seen as a pattern repeated throughout the campaign is that ISIS leaders begin to leave areas they expect to lose...” Dorrian said.

One British man, his wife, and an American man surrendered to Turkish border officials in Killis after leaving Syria last week, the Guardian reported.

Dorrian explained that the tactics used by foreigners is partially enabled because of their anonymity within the communities.

"We've seen them do things like light a bunch of oil fires in Qayyara, we've seen them light a sulphur plant on the road to Mosul,” Dorrian said, generally referring to foreign fighters and leaders.

"They are holding people who are trying to leave,” he added. “These are the types of things that are easy to do when the people are not your neighbors, and not people you've grown up with or people you know very well.”

Kary Paul Kleman, the American, previously lived in Florida, according to CNN.

A US official confirmed to CNN that Kleman was arrested trying to cross back into Turkey through Killis alongside a British national and that man's wife.

The Guardian reported the Briton was Stefan Aristidou from London, and his unnamed wife is said to be of Bangladeshi heritage. 

Both men could be subject to terrorism charges, in-line with British and US laws, and precedent of similar cases.

"The Iraqi security has taken control of some of these people and worked with Coalition partners if those people are from those countries to share information and intelligence about that,” Dorrian said.

The two major cities still held by ISIS are Mosul in Iraq, and Raqqa in Syria, which the coalition estimates contain fewer than 1,000 and around 3,000 to 4,000 militants, respectively.